- Home
- Diabetes Information for Patients Types Symptoms Tests and Treatment
- How to Manage Flu When You Have Diabetes
Flu and Diabetes: How to Stay Safe During Flu Season
Flu and diabetes can be a difficult combination. Influenza may raise blood sugar through illness and stress hormones, while poor appetite, vomiting, or continued diabetes medicine without enough food may cause blood sugar to fall. Dehydration can make both problems more dangerous.
As I explain to my patients, diabetes does not necessarily mean that you will catch influenza more often than everyone else. The important concern is that people with type 1, type 2, or gestational diabetes have a higher risk of serious flu complications—even when diabetes is usually well managed.
Quick Answer
If you have diabetes, get an age-appropriate injectable flu vaccine every season unless your healthcare professional identifies a contraindication. If flu symptoms begin, contact your clinician promptly because diabetes places you in a group for whom early prescription antiviral treatment is recommended. Follow your written sick-day plan, check glucose more often, check ketones when advised, stay hydrated, and seek urgent care for breathing difficulty, confusion, severe dehydration, or inability to keep fluids down.
Why Is Flu More Serious When You Have Diabetes?
Diabetes is an endocrine condition associated with a higher risk of serious influenza complications. These may include pneumonia, bronchitis, sinus or ear infections, worsening heart or kidney disease, severe dehydration, diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS), hospitalization, and—in severe cases—death.
This does not mean every person with diabetes has a “weak immune system,” and it does not mean a complication will happen. Risk varies with age, glucose control, pregnancy, vaccination status, kidney or heart disease, lung disease, obesity, smoking, frailty, and how quickly treatment begins.
How influenza can affect blood sugar
When the body fights an infection, it releases hormones that can make insulin work less effectively and prompt the liver to release more glucose. Blood sugar may therefore rise even when you are eating less than usual. Fever and faster breathing also increase fluid loss, and high glucose causes additional urination, making dehydration more likely.
Blood sugar can also fall. This is more likely if you cannot eat, vomit, have diarrhea, or continue taking insulin or a medicine that can cause hypoglycemia without following your sick-day instructions. For this reason, the flu may cause high readings, low readings, or rapid changes between the two.
Who needs extra caution?
- People with type 1 diabetes or a history of DKA
- People using insulin, sulfonylureas, or other medicines that can cause low blood sugar
- People taking an SGLT2 inhibitor, because illness and reduced food intake can increase DKA risk
- Pregnant people, including those with gestational diabetes
- Children, older adults, and people who live alone
- People with kidney, heart, lung, neurologic, or immune conditions
- People with previous severe influenza or pneumonia
- Anyone who cannot monitor glucose, drink safely, or manage medicines during illness
Flu Symptoms in People With Diabetes
Influenza often begins more suddenly than a common cold, but symptoms vary. A person can have flu without a fever. Common symptoms include:
- Fever or feeling feverish and chilled
- Cough
- Sore throat
- Runny or blocked nose
- Muscle or body aches
- Headache
- Marked tiredness
- Vomiting or diarrhea, which is more common in children
Flu, COVID-19, and other respiratory infections can look similar, and symptoms alone may not identify the virus. Depending on local circulation and your health, your clinician may recommend testing. Do not delay contacting a clinician about treatment simply because a home test is unavailable or an early test is negative.
Call your healthcare professional promptly
If you have diabetes and develop suspected flu symptoms, contact your clinician the same day when possible. Tell them when symptoms began, your temperature, glucose pattern, ketone result if relevant, diabetes type, medicines, kidney function, pregnancy status, and whether you can eat and drink.
Prompt contact matters because prescription flu antivirals work best when started early. You do not need to wait until you are extremely ill before asking for medical advice.
Flu Vaccine and Diabetes
Annual influenza vaccination is the most important preventive step. The vaccine is updated because circulating influenza viruses change and protection decreases over time. In the United States, the CDC recommends seasonal flu vaccination for everyone aged six months and older, with rare exceptions, and emphasizes vaccination for people at increased risk of complications, including those with diabetes.
Recommendations and vaccine availability differ between countries, so follow your national program and clinician’s advice. For many people who need one dose, vaccination during September or October provides useful timing before influenza activity increases. Vaccination can still be beneficial later while flu viruses are circulating.
Can the flu shot give me influenza?
No. Injectable inactivated and recombinant influenza vaccines do not contain live influenza virus capable of causing flu. Temporary soreness, fatigue, headache, or a mild fever can occur as the immune system responds. Protection takes about two weeks to develop, and the vaccine cannot prevent every respiratory infection, but it can reduce influenza illness and serious complications.
What if I am pregnant or have gestational diabetes?
Pregnancy and gestational diabetes both increase the importance of prevention and early treatment. Pregnant people should receive an injectable influenza vaccine rather than the nasal spray, unless their obstetric clinician identifies a contraindication. Timing may be individualized according to the stage of pregnancy and local recommendations.
Pneumococcal vaccination is separate
A pneumococcal vaccine does not prevent influenza. It protects against certain pneumococcal infections, including some forms of pneumonia that can occur as a flu complication. People with diabetes should ask whether they are up to date with pneumococcal vaccination according to their age, previous doses, and national schedule.
Ways to Reduce Your Risk During Flu Season
Vaccination is central, but several everyday habits provide additional protection:
- Avoid close contact with people who are acutely ill when possible.
- Wash hands with soap and water, especially before eating or touching your face.
- Use alcohol-based hand sanitizer when soap and water are not available.
- Cover coughs and sneezes and dispose of tissues promptly.
- Improve indoor air by opening windows or using suitable ventilation or filtration when practical.
- Clean frequently touched surfaces when someone at home is ill.
- Keep enough diabetes medicines, testing supplies, ketone strips, fluids, and easy-to-tolerate foods at home.
- Know how to contact your diabetes team outside routine office hours.
Sleep, nutritious food, movement, and glucose management support overall health, but they do not replace influenza vaccination or antiviral treatment when indicated. No vitamin, tea, herbal product, or supplement has been proven to prevent influenza in place of vaccination.
Antiviral Treatment for Flu and Diabetes
Flu antivirals are prescription medicines that act against influenza viruses. They are not antibiotics, and over-the-counter cold remedies are not substitutes for them. The CDC recommends prompt antiviral treatment for people with confirmed or suspected flu who are at increased risk of complications, including people with type 1, type 2, or gestational diabetes.
Treatment works best when started within one to two days after symptoms begin. However, people who are hospitalized, seriously ill, getting worse, or at high risk may still benefit when treatment begins later. Your clinician may start treatment based on symptoms and local flu activity without waiting for a positive test.
Choosing an antiviral
The appropriate medicine depends on age, pregnancy, kidney function, asthma or lung disease, other medicines, symptom duration, and local influenza resistance. Oseltamivir is commonly used, but it is not the only option. Some antivirals require dose adjustment in kidney disease, and inhaled products are not appropriate for everyone.
Diabetes Sick-Day Rules for Flu
Your sick-day plan should be written before flu season. It needs to explain how often to monitor, which medicines to continue, which may need to be paused, how to replace fluids and carbohydrate, when to check ketones, and when to call for help.
- Contact your clinician early. Ask about antiviral treatment and confirm which diabetes medicines to take while you are eating or drinking less.
- Check glucose more often. A common starting point is about every four hours, including overnight when advised, but follow your personal plan. CGM users should keep a meter available if symptoms do not match the sensor.
- Check ketones when instructed. This is especially important in type 1 diabetes, pregnancy, persistent high glucose, pump failure, vomiting, abdominal pain, or possible DKA.
- Keep drinking. Take frequent small sips. Choose sugar-free fluids when glucose is high, or carbohydrate-containing fluids when you cannot eat and your plan says carbohydrate is needed.
- Record important information. Write down glucose, ketones, temperature, medicines, fluids, urine output, vomiting, and when symptoms began.
- Know your escalation point. Do not wait until severe dehydration, confusion, or breathing difficulty develops.
- Glucose meter, strips, lancets, and batteries
- CGM and pump backup supplies
- Blood or urine ketone strips
- Insulin, syringes, or pens and a backup dose plan
- Fast-acting glucose and prescribed glucagon
- Thermometer
- Sugar-free and carbohydrate-containing fluids
- Easy-to-tolerate carbohydrate foods
- Medication list and clinician contact details
- Written sick-day and emergency plan
Should you continue insulin?
If you have type 1 diabetes, do not stop basal insulin simply because you are not eating. Illness may increase insulin needs and stopping basal insulin can lead to DKA. Use only the correction instructions supplied by your diabetes team and call if you cannot follow the plan safely.
People with type 2 or gestational diabetes also need individualized instructions. Some medicines may need temporary adjustment or withholding during vomiting, dehydration, reduced food intake, kidney problems, or severe illness. This can include metformin, SGLT2 inhibitors, sulfonylureas, and other treatments depending on the situation. Do not make a blanket decision to continue or stop every diabetes medicine; follow the written plan or contact a clinician.
For a fuller explanation of basal insulin, correction dosing, ketones, and pump failure, review our guide to insulin treatment and illness safety.
What should you drink and eat?
Take small, frequent sips rather than trying to drink a large amount at once. Water, broth, or another sugar-free drink may be appropriate when glucose is high. If you cannot eat and glucose is normal or falling, your plan may recommend a drink or soft food that contains carbohydrate. Examples can include measured juice, milk, oral rehydration drink, soup, yogurt, crackers, or toast, depending on tolerance and glucose.
Do not force large meals. The immediate goals are safe hydration, enough carbohydrate to prevent hypoglycemia when needed, and appropriate insulin. If you cannot keep fluids down, seek medical advice urgently.
Ketones and diabetic ketoacidosis
Ketones can rise when the body does not have enough insulin. Check them according to your plan if glucose is persistently high, you are vomiting, you have abdominal pain, your insulin pump may have failed, or you feel unusually ill.
People using an SGLT2 inhibitor can develop DKA with glucose that is lower than expected. If you take empagliflozin, dapagliflozin, canagliflozin, or another SGLT2 inhibitor and develop nausea, vomiting, abdominal pain, rapid breathing, marked fatigue, or positive ketones, seek urgent medical advice even if the glucose number is not extremely high.
Use our guide to dangerous blood sugar levels and ketone warnings to understand when a reading becomes more concerning.
Cold and Flu Medicines With Diabetes
Over-the-counter products may relieve symptoms, but combination medicines can contain several active ingredients. Some liquid products contain sugar; decongestants may raise blood pressure or heart rate; anti-inflammatory medicines may be unsuitable in kidney disease, dehydration, stomach ulcers, heart disease, or with certain prescriptions.
- Ask a pharmacist to check the exact product against your diabetes, kidney function, blood pressure, pregnancy status, and current medicines.
- Read the active-ingredient list, not only the brand name.
- Avoid taking two products that both contain acetaminophen/paracetamol.
- Choose a sugar-free preparation when suitable, but remember that “sugar-free” does not guarantee that the medicine is safe for you.
- Check whether any medicine or supplement can interfere with your glucose meter or CGM model.
- Do not use cough or cold medicine in a child without age-appropriate medical advice.
When Flu and Diabetes Need Urgent Medical Care
Contact your diabetes or primary-care team promptly if readings remain outside your target, you have ketones, fever persists, symptoms are worsening, you cannot follow your medicine plan, or you are unsure how to replace fluids and carbohydrate.
Get Emergency Help Now
Seek emergency care immediately for difficulty breathing, shortness of breath, persistent chest or abdominal pain, confusion, inability to wake, seizure, severe weakness or unsteadiness, no urine or signs of severe dehydration, bluish lips or face, repeated vomiting, inability to keep fluids down, moderate or high ketones, deep or rapid breathing, fruity-smelling breath, or glucose that remains dangerously high despite following the prescribed plan.
Also get urgent help if fever or cough improves and then returns or becomes worse, or if diabetes, heart disease, kidney disease, or another chronic condition suddenly deteriorates.
| Situation | What to do | Why it matters |
|---|---|---|
| New flu symptoms | Call your clinician promptly and ask about antiviral treatment. | People with diabetes are at increased risk, and treatment works best when started early. |
| Glucose below 70 mg/dL (3.9 mmol/L) | If awake and able to swallow, follow your hypoglycemia treatment plan and recheck. | Poor intake and some diabetes medicines can cause a dangerous low. |
| Persistent high glucose | Follow the written correction and ketone plan; call if readings do not improve. | Infection, dehydration, or insufficient insulin can lead to DKA or HHS. |
| Vomiting or inability to drink | Seek urgent medical advice; do not wait for routine office hours if worsening. | Dehydration and metabolic emergencies can develop quickly. |
| Breathing difficulty, confusion, seizure, or inability to wake | Call local emergency services immediately. | These can indicate a severe respiratory or diabetes emergency. |
Doctor’s Note
If you have diabetes, I recommend preparing for flu season before you become ill. Keep the current vaccine, a two-week reserve of essential diabetes supplies when practical, a written sick-day plan, and the contact number for prompt medical advice. The safest approach is not to panic, but to act early—especially when antiviral treatment, hydration, ketone testing, or medicine adjustment may be needed.
Frequently Asked Questions
Do people with diabetes catch flu more easily?
Not necessarily. The clearest established concern is that people with type 1, type 2, or gestational diabetes have a higher risk of serious flu complications. Glucose can also become harder to manage during infection.
Should everyone with diabetes get a flu vaccine?
Annual injectable influenza vaccination is recommended for most people with diabetes aged six months and older, unless there is a specific contraindication. The appropriate product depends on age, pregnancy, allergies, previous reactions, health conditions, and national guidance.
Can the flu shot raise blood sugar?
Some people may have a temporary stress response, mild fever, or reduced activity after vaccination, which can briefly affect glucose. This is usually mild. Monitor according to your normal plan and contact your clinician for persistent high readings, ketones, severe symptoms, or an allergic reaction.
Can an injectable flu vaccine cause influenza?
No. Injectable inactivated and recombinant influenza vaccines do not contain live influenza virus capable of causing flu. Mild soreness, fatigue, headache, or fever can occur after vaccination.
When should a person with diabetes ask for flu antivirals?
Contact a clinician as soon as flu symptoms begin. Diabetes is a high-risk condition for flu complications, and prompt prescription antiviral treatment is recommended for confirmed or suspected influenza. Treatment works best within 48 hours, but it may still help later in high-risk or seriously ill patients.
How often should I check blood sugar when I have flu?
A common sick-day starting point is about every four hours, but your plan may require more frequent checks based on diabetes type, medicines, pregnancy, CGM use, symptoms, and glucose pattern. Follow the schedule from your diabetes team.
Should I stop insulin if I cannot eat?
Do not stop basal insulin in type 1 diabetes simply because you are not eating. This can cause DKA. Other doses and diabetes medicines may need adjustment, so use your written plan or contact your clinician promptly.
When should I go to the emergency room?
Seek emergency care for breathing difficulty, persistent chest or abdominal pain, confusion, seizure, inability to wake, severe dehydration, no urine, repeated vomiting, inability to keep fluids down, moderate or high ketones, deep or rapid breathing, or dangerously high glucose that is not improving.
Related Questions and Resources
References
- Centers for Disease Control and Prevention. Flu and People with Diabetes.
- Centers for Disease Control and Prevention. 2026–2027 Flu Season.
- Centers for Disease Control and Prevention. Who Needs a Flu Vaccine.
- Centers for Disease Control and Prevention. Live Attenuated Influenza Vaccine (Nasal Spray).
- Centers for Disease Control and Prevention. Treating Flu with Antiviral Drugs.
- Centers for Disease Control and Prevention. Managing Sick Days.
- Centers for Disease Control and Prevention. Diabetic Ketoacidosis.
- Centers for Disease Control and Prevention. Signs and Symptoms of Flu.
Medical disclaimer: This page provides general diabetes and influenza education. It does not replace vaccination advice, diagnosis, antiviral prescribing, medicine adjustment, a personal sick-day plan, or emergency care from your healthcare professional. If symptoms are severe, breathing is difficult, ketones are elevated, or you cannot keep fluids down, seek urgent medical care.